If you have a sweet tooth and that is what is causing the overeating and possibly the weight gain, consider stopping all sugar. For many people, if they do not eat it, they do not crave it. Some people find they need to give up fruit and artificial sweeteners too, but I didn't find that personally.
Keep the sweets OUT OF YOUR HOUSE! If someone else in your house NEEDS sweets, have them eat them somewhere not around you and ask them to put them in a certain cupboard that you don't go into, or keep them in their car or something.
Probably you have not stretched your stomach. You don't need to "shrink" your stomach (and really, there is no way to do that). You need to find a way to avoid the foods that cause you to overeat. Can you distract yourself when you have a craving? Talk a walk, watch a YouTube exercise video, take a hot shower/bath, read a book, color, etc? For many people, once they wait an hour by distracting themselves, they usually can make it without eating.
You may also consider meeting with a therapist who specializes in eating disorder, or call your original surgery center for help. I have noticed that not everyone has these options, but you do have the option to avoid sweets (I have a sweet tooth too, so I understand!)
Good luck!